CS8281
5.0 V/250 mA, 5.0 V/100 mA
Micropower Low Dropout
Regulator with ENABLE
The CS8281 is a precision, dual 5.0 V micropower linear voltage
regulator. The switched primary output (V
OUT1
) supplies up to 250 mA
while the secondary (V
OUT2
) is capable of supplying 100 mA. Both
outputs have a maximum dropout voltage of 600 mV and low reverse
current. Quiescent current drain is typically 150
µA
when supplying
100
µA
from each output.
The ENABLE input provides logic level control of the primary
output. With the primary output disabled, quiescent current drain is
typically 100
µA
when supplying 100
µA
from the secondary output.
The CS8281 is extremely robust with protection provided for
reverse battery, short circuit, overvoltage, and overtemperature on
both outputs.
The CS8281 is available in a 5–lead D
2
PAK.
Features
•
5.0 V/250 mA Primary Output
•
5.0 V/100 mA Secondary Output
•
3.0% Tolerance, Both Outputs
•
ON/OFF Control for Primary Output
•
Low Quiescent Current Drain (100
µA
V
OUT2
)
•
Low Reverse Current
•
Protection Features
–
Reverse Battery (–15 V)
–
74 V Load Dump
–
Short Circuit
–
Overtemperature
–
Overvoltage (34 V)
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1
5
D
2
PAK
5–PIN
DP SUFFIX
CASE 936F
PIN CONNECTIONS AND
MARKING DIAGRAM
Tab = GND
Pin 1. V
IN
2. V
OUT1
3. GND
4. V
OUT2
5. ENABLE
CS8281
AWLYWW
1
A
WL, L
YY, Y
WW, W
= Assembly Location
= Wafer Lot
= Year
= Work Week
ORDERING INFORMATION*
Device
CS8281YDP5
CS8281YDPR5
Package
D
2
PAK,
5–PIN
D2PAK,
5–PIN
Shipping
50 Units/Rail
750 Tape & Reel
*Consult your local sales representative for SO–8,
SO–16, DIP–8, DIP–16, TO–220 FIVE LEAD, and
D
2
PAK 7–PIN packaging options.
©
Semiconductor Components Industries, LLC, 2001
1
January, 2001 – Rev. 6
Publication Order Number:
CS8281/D
CS8281
Primary Output
V
IN
V
OUT1
ENABLE
+
–
+
–
Current Limit
V
OUT1
SENSE
Bandgap
Reference
Overvoltage
Shutdown
Thermal
Shutdown
Secondary Output
V
OUT2
Current Limit
+
–
V
OUT2
SENSE
Pwr GND
GND
Figure 1. Block Diagram
ABSOLUTE MAXIMUM RATINGS*
Rating
Input Voltage
Power Dissipation
Operating Temperature Range
Maximum Junction Temperature
Storage Temperature Range
Electrostatic Discharge (Human Body Model)
Lead Temperature Soldering
1. 16 second maximum above 183°C
*The maximum package power dissipation must be observed.
Reflow (SMD styles only) (Note 1.)
Value
–15 to 74
Internally Limited
–40 to +125
–40 to +150
–55 to +150
4.0
230 peak
Unit
V
–
°C
°C
°C
kV
°C
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2
CS8281
ELECTRICAL CHARACTERISTICS:
(6.0 V
≤
V
IN
≤
26 V, I
OUT1
= I
OUT2
= 100
µA,
–40°C
≤
T
C
≤
125°C;
unless otherwise specified.)
Characteristic
Primary Output Stage (V
OUT1
)
Output Voltage, V
OUT1
Dropout Voltage
Line Regulation
Load Regulation
Quiescent Current
Ripple Rejection
Current Limit
Short Circuit Current Limit
Reverse Current
Secondary Output (V
OUT2
)
Output Voltage, (V
OUT2
)
Dropout Voltage
Line Regulation
Load Regulation
Quiescent Current
Ripple Rejection
Current Limit
Short Circuit Current Limit
Reverse Current
ENABLE Function (ENABLE)
Input Threshold
Input Bias Current
Protection Circuits
Overtemperature Threshold
Overvoltage Shutdown
–
–
150
30
180
34
–
38
°C
V
ENABLE = LOW, 7.0 V
≤
V
IN
≤
26 V
ENABLE = HIGH, 7.0 V
≤
V
IN
≤
26 V
0 V
≤
V
ENABLE
≤
5.0 V
–
2.0
–2.0
1.2
1.2
0
0.8
–
2.0
V
V
µA
100
µA ≤
I
OUT1
≤
100 mA
I
OUT2
= 100 mA
I
OUT2
= 100
µA
6.0 V
≤
V
IN
≤
26 V
100
µA ≤
I
OUT2
≤
100 mA, V
IN
= 14 V
ENABLE = LOW, V
IN
= 12.8 V
ENABLE = HIGH, V
IN
= 16 V
f = 120 Hz; I
OUT2
= 50 mA, 7.0 V
≤
V
IN
≤
17 V
–
V
OUT2
= 0 V, V
IN
= 16 V, I
OUT1
= 0 A
V
OUT2
= 5.0 V, V
IN
= 0 V
4.85
–
–
–
–
–
60
105
25
–
5.00
400
100
5.0
5.0
100
8.0
70
200
–
100
5.15
600
150
50
50
150
25
–
–
–
250
V
mV
mV
mV
mV
µA
mA
dB
mA
mA
µA
V
OUT1
= 0 V, V
IN
= 16 V
V
OUT1
= 5.0 V, V
IN
= 0 V
100
µA ≤
I
OUT1
≤
250 mA
I
OUT1
= 250 mA
I
OUT1
= 100
µA
6.0 V
≤
V
IN
≤
26 V
1.0 mA
≤
I
OUT1
≤
250 mA, V
IN
= 14 V
ENABLE = HIGH, V
IN
= 16V, I
OUT1
= 250 mA
f = 120 Hz, I
OUT1
= 125 mA, 7.0 V
≤
V
IN
≤
17 V
–
4.85
–
–
–
–
–
60
260
25
–
5.00
400
100
5.0
5.0
22
70
400
–
100
5.15
600
150
50
50
50
–
–
–
1500
V
mV
mV
mV
mV
mA
dB
mA
mA
µA
Test Conditions
Min
Typ
Max
Unit
PACKAGE PIN DESCRIPTION
PACKAGE LEAD #
D
2
PAK, 5–PIN
1
2
3
4
5
LEAD SYMBOL
V
IN
V
OUT1
GND
V
OUT2
ENABLE
FUNCTION
Supply voltage to IC, usually direct from battery.
5.0 V regulated output which is activated by ENABLE input.
Ground connection.
Standby output 5.0 V, 100 mA capability; always on.
CMOS compatible input lead; switches V
OUT1
. When ENABLE
is high, V
OUT1
is active.
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3
CS8281
DEFINITION OF TERMS
Current Limit
– Peak current that can be delivered to the
output.
Dropout Voltage
– The input–output voltage differential
at which the circuit ceases to regulate against further
reduction in input voltage. Measured when the output
voltage has dropped 100 mV from the nominal value
obtained at 14 V input, dropout voltage is dependent upon
load current and junction temperature.
Input Output Differential
– The voltage difference
between the unregulated input voltage and the regulated
output voltage for which the regulator will operate.
Input Voltage
– The DC voltage applied to the input
terminals with respect to ground.
Line Regulation
– The change in output voltage for a
change in the input voltage. The measurement is made under
conditions of low dissipation or by using pulse techniques
such that the average chip temperature is not significantly
affected.
60 V
V
IN
14 V
34 V
3.0 V
26 V
Load Regulation
– The change in output voltage for a
change in load current at constant chip temperature.
Long Term Stability
– Output voltage stability under
accelerated life–test conditions after 1000 hours with
maximum rated voltage and junction temperature.
Quiescent Current
– The part of the positive input
current that does not contribute to the positive load current,
i.e., the regulator ground lead current.
Ripple Rejection
– The ratio of the peak–to–peak input
ripple voltage to the peak–to–peak output ripple voltage.
Short Circuit Current Limit
– Peak current that can be
delivered by the outout when forced to 0 V.
Temperature Stability of V
OUT
– The percentage
change in output voltage for a thermal variation from room
temperature to either temperature extreme.
14 V
ENABLE
2.0 V
0.8 V
0V
0V
5.0 V
5.0 V
2.4 V
5.0 V
0V
5.0 V
0V
5.0 V
0V
5.0 V
5.0 V
0V
V
OUT1
V
OUT2
5.0 V
5.0 V
2.4 V
5.0 V
5.0 V
5.0 V
System
Condition
Turn
On
Load
Dump
Low V
IN
Line
Noise, Etc.
V
OUT1
Short
Circuit
V
OUT2
Short
Circuit
Thermal
Shutdown
Turn
Off
Figure 2. Typical Circuit Waveform
APPLICATION NOTES
General
The CS8281 is a micropower dual 5.0 V regulator. All bias
required to operate the internal circuitry is derived from the
standby output, V
OUT2
. If this output experiences an over
current situation and collapses, then V
OUT1
will also
collapse (see Figure 2).
If there is critical circuitry that must remain active under
most conditions it should be connected to V
OUT2
. Any
circuitry that is likely to be subjected to a short circuit, e.g.,
circuitry outside the module, should be connected to V
OUT1
.
External Capacitors
Output capacitors are required for stability with the
CS8281. Without them, the regulator outputs will oscillate.
Actual size and type may vary depending upon the
application load and temperature range. Capacitor effective
series resistance (ESR) is also a factor in the IC stability.
Worst–case is determined at the minimum ambient
temperature and maximum load expected.
Output capacitors can be increased in size to any desired
value above the minimum. One possible purpose of this
would be to maintain the output voltages during brief
conditions of negative input transients that might be
characteristic of a particular system.
Capacitors must also be rated at all ambient temperatures
expected in the system. To maintain regulator stability down
to –40°C, capacitors rated at that temperature must be used.
More information on capacitor selection for SMART
REGULATOR®s is available in the SMART REGULATOR
application note, “Compensation for Linear Regulators,”
document number SR003AN/D, available through the
Literature Distribution Center or via our website at
http://www.onsemi.com.
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4
CS8281
ENABLE
The ENABLE function controls V
OUT1
. When ENABLE
is high, V
OUT1
is on. When ENABLE is low, V
OUT1
is off.
Calculating Power Dissipation in a
Dual Output Linear Regulator
I
IN
V
IN
SMART
REGULATOR
I
OUT1
V
OUT1
The maximum power dissipation for a dual output
regulator (Figure 3) is
PD(max)
+
VIN(max)
*
VOUT1(min) IOUT1(max)
)
VIN(max)
*
VOUT2(min) IOUT2(max)
)
VIN(max)IQ
(1)
Control
Features
I
OUT2
V
OUT2
I
Q
where:
V
IN(max)
is the maximum input voltage,
V
OUT1(min)
is the minimum output voltage from V
OUT1
,
V
OUT2(min)
is the minimum output voltage from V
OUT2
,
I
OUT1(max)
is the maximum output current, for the
application,
I
OUT2(max)
is the maximum output current, for the
application, and
I
Q
is the quiescent current the regulator consumes at both
I
OUT1(max)
and I
OUT2(max)
.
Once the value of P
D(max)
is known, the maximum
permissible value of R
ΘJA
can be calculated:
R
QJA
+
150°C
*
TA
PD
(2)
Figure 3. Dual Output Regulator With Key
Performance Parameters Labeled.
Heat Sinks
A heat sink effectively increases the surface area of the
package to improve the flow of heat away from the IC and
into the surrounding air.
Each material in the heat flow path between the IC and the
outside environment will have a thermal resistance. Like
series electrical resistances, these resistances are summed to
determine the value of R
ΘJA:
R
QJA
+
R
QJC
)
R
QCS
)
R
QSA
(3)
The value of R
ΘJA
can be compared with those in the
package section of the data sheet. Those packages with
R
ΘJA
’s less than the calculated value in equation 2 will keep
the die temperature below 150°C.
In some cases, none of the packages will be sufficient to
dissipate the heat generated by the IC, and an external
heatsink will be required.
where:
R
ΘJC
= the junction–to–case thermal resistance,
R
ΘCS
= the case–to–heatsink thermal resistance, and
R
ΘSA
= the heatsink–to–ambient thermal resistance.
R
ΘJC
appears in the package section of the data sheet. Like
R
ΘJA
, it too is a function of package type. R
ΘCS
and R
ΘSA
are functions of the package type, heatsink and the interface
between them. These values appear in heat sink data sheets
of heat sink manufacturers.
TEST & APPLICATION DIAGRAM
V
IN
0.1
µF
V
BATT
V
OUT1
22
µF
ESR < 8
Ω
Load
GND
C
3
**
C
1
*
CS8281
V
OUT2
C
2
**
22
µF
ESR < 8
Ω
V
CC
mP
ENABLE
I/O
GND
* C
1
required if regulator is located far from power supply filter.
** C
2
and C
3
required for stability. Capacitor must operate at minimum temperature expected during system operations.
Figure 4. Test & Application Circuit
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